Cobalt base alloys



United States Patent 3,113,763 CfiEALT BASE ALLGYS Rudolf H. Thielemann,Palo Alto, Calif., assignor to Sierra M'etals Corporation, Chicago, IlL,a corporation of Delaware No Drawing. Filed July 28, 1958, Ser. No.751,159 9 Genus. (Cl. 75171) This invention relates to a cobalt basemetal alloy which includes alloying metal additives which make theresulting alloy corrosion resistant and of great mechanical workstrength at temperatures between about l500 F. and about 220G" F.

Important features of the alloy of this invention are that it may becast, is highly resistant to oxidation and other forms of corrosion, andpossesses great mechanical strength at temperatures up to between aboutl500 F. and about 2200" F. As a result, this alloy may be used asblades, vanes, and other parts of high temperature gas turbine engines.Other important uses of the alloy of this invention are as exhaustvalves and manifolds in internal combustion engines, heat exchanges, aslinings for retorts and container vessels used in the chemical andmetallurgical industries, and as an oxidation resistant coating materialfor metals and metal alloys such as columbium, tantalum, nickel basealloys, cobalt base alloys, etc., which possess high strengthcharacteristics at elevated temperatures but whose resistance tooxidation at elevated temperatures, i.e., above about 1500 F., isinadequate. The alloy of this invention can also be utilized as hightemperature, high strength, corrosion resistant tubing and sheetmaterial, as a material for forming cutting blades useful for cuttingmolten glass and other hot corrosive materials, as a material forforming supporting members or holders for use in metallurgical testingapparatus, etc.

The priorart nickel and/ or cobalt base metal alloys which have beenused as blades, vanes, and other parts of hi h temperature gas turbineengines, have a maximum operating temperature of about 1580" F. Forexample, a common nickel-cobalt base metal alloy which incorporatesmolybdenum as a constituent is for all practical purposes non-utilizableas a structural member a gas turbine engine if the metal temperature isabove l500 F. One reason for this temperature limit is that theoxidation resistance of such an alloy fails above 1500 F.

An alloy of this invention when used as a blade or vane in a high ternerature as turbine engine can be operated at markedly highertemperatures than was possible heretofore. The performance of gasturbine engines incorpo rating such blades or vanes is considerablyimproved, since at higher temperatures the total thrust of a gas turbineengine increases and the amount of fuel consumed per pound of thrustdecreases.

The metal alloy of this invention is comprised, by Weight, of thefollowing constituents: from about 15 to about 28 percent of chromium;from about to about percent of tungsten; from about 0.5 to about percentof tantalum; from about 0.01 to about 3 percent of titanium; from about0.1 to about 1.3 percent of carbon; and the balance being essentiallycobalt.

I have found that the high temperature corrosion resistant properties ofthe alloy of this invention are not ice affected if the alloy includesan amount of columbium which is not more than one-half of the amount oftantalum in the alloy and, in any event, is no greater than 3 percent,by weight, of the alloy, and preferably not more than 2.0 percent, byweight, of the alloy.

It is important to note that in the past the metals tantalum andcolumbium have been considered to be equivalent for various purposes.This is not true in the case of the alloy of this invention. Forexample, if in the alloy of this invention, columbium is substituted fortantalum in the range of proportions specified, the resulting alloy doesnot possess the high temperature corrosion resistance characteristic ofthe alloy of this invention.

While molybdenum is not a primary constituent of the alloy of thisinvention, I have found that the properties of the alloy of thisinvention are not deleteriously affected if the alloy includes an amountof molybdenum which is not more than one-half the amount of tungsten inthe alloy and, in any event, is no greater than 3.5 percent, by Weight,of the alloy.

I have also found that zirconium may be tolerated in the alloy of thisinvention in an amount such that if the amount or" titanium in the alloyis more than about 0.5 percent, the combined amount of titanium andzirconium is equal to or less than about 3 percent, and if the amount oftitanium is equal to or less than about 0.5 percent, the amount oftitanium is more than about percent of the amount of zirconium in thealloy.

It has been further found that the inclusion of any one or more of thefollowing ingredients: up to about 0.2 percent of boron, up to about 1.5percent of silicon, and up to about 5 percent of nickel and/or iron mayin certain formulations improve various metallurgical characteristics ofthe alloy. Additional amounts of these ingredients may in some cases betolerated in the alloy without deleterious effects.

It is to be noted that if the boron content in the alloy of thisinvention exceeds about 0.2 percent, then the alloy of this inventionbecomes unsatisfactory, particularly in those applications Where thermalshock requirements are important.

To achieve the optimum desired properties, it is preferred that thefollowing impurities which may be in the alloy be held to the followinglimits by weight. The manganese content in the final alloy should not begreater than about 2 percent. The interstitial elements such asnitrogen, hydrogen, tin, lead, and the like should be kept as low aspossible. In addition, not more than about 0.5 percent total ofdeoxidizers such as calcium, magnesium, and the like should be presentin the final alloy.

A preferred range of proportions of constituents of the alloy of thisinvention which has especially high oxidation resistance and strengthcharacteristics, at temperatures of 2000 F., and above, and which isparticularly suitable for use as a vane material in a gas turbine, hightemperature engine is as follows: from about 16 to about 25 percent ofchromium; from about 7.5 to about 12.5 percent of tungsten; from about 7to about 11 percent of tantalum; from about .08 to about 0.5 percent oftitanium; from about 0.6 to about 1.0 percent of carbon; and the balancebeing essentially cobalt.

Following are examples of the preparation and test results of the cobaltbase metal alloy of this invention.

Example 1 A 5 pound alloy melt of a cobalt base metal alloy compositioncontaining about 20 percent of chromium, about 11 percent of tungsten,about 1.5 percent of tantalum, about 1.5 percent of titanium, about 0.1percent of carbon, and the balance essentially cobalt, all percentagesby weight, was prepared by melting the chromium and cobalt in a magnesiacrucible under high vacuum conditions, following which the tungsten,tantalum, titanium, and carbon in the form of graphite were added.

A cluster of 6 test bars were formed from the 5 pound melted alloy heatand cast by the usual investment casting technique, under high vacuumconditions. These bars were each 3 inches long and A inch in diameter.

The test bars of this example had an elongation of 10 percent at roomtemperature under a tensile stress of 95,000 p.s.i. V

The test bars of this example had a rupture life in excess of 100 hoursunder a load of 12,000 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 100 hours under a load of 10,000 p.s.i.at a temperature of about 1800 F. in air.

Example 2 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 28 percent of chromium, about 5 percent of tungsten,about 1.5 percent of tantalum, about 1.5 percent of titanium, about 0.4percent of carbon, and the balance essentially cobalt, all percentagesby weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 3 percent at roomtemperature under a tensile stress of 100,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hoursunder a load of 15,000 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 100 hours under a load of 8,000 p.s.i.at a temperature of about 1800 F. in air.

Example 3 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about percent of chromium, about 11 percent of tungsten,about 0.5 percent of tantalum, about 3 percent of titanium, about 0.7percent of carbon, and the balance essentially cobalt, all percentagesby weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 7 percent at roomtemperature under a tensile stress of 115,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hoursunder a load of 15,000 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 100 hours under a load of 10,000 p.s.i.at a temperature of about 1800 F. in air. 7

Example 4 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 20 percent of chromium, about 10 percent of tungsten,about 10 percent of tantalum, about 0.3 percent of titanium, about 1.0percent excess of hours under a load of 18,000 p.s.i. at a temperatureof about 1700 F. in air, and a rupture life in excess of 100 hours undera load of 12,000 p.s.i. at a temperature of about 1800 F. in air.

Example 5 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 15 percent of chromium, about 15 percent of tungsten,about 13 percent of tantalum, about 0.01 percent of titanium, about 0.65percent of carbon, and the balance essentially cobalt, all percentagesby weight, were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 5 percent at roomtemperature under a tensile stress of 124,000 p.s.i.

The test bars of this example'had a rupture life in excess of 100 hoursunder a load of 25,000 p.s.i. at a temperature of about 1600 F. in air,a rupture life in excess of 100 hours under a load of 18,000 p.s.i. at atemperature of about 1700 F. in air, and a rupture life in excess of 100hours under a load of 10,000 p.s.i. at a. temperature of about 1800" F.in air.

Example 6 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 20 percent of chro mium, about 10 percent of tungsten,about 20 percent of tantalum, about 2 percent of titanium, about 1percent of zirconium, about 0.85 percent of carbon, and the balanceessentially cobalt, all percentages by weight, were prepared in the samemanner as set forth in Example 1.

The test bars of this example had an elongation of 6 percent at roomtemperature under a tensile stress of 118,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hoursunder a :load of 20,000 p.s.i. at a temperature of about 1600" F. inair, a rupture life in excess of 100 hours under a load of 15,000 p.s.i.at a temperature of about 1700 F. in air, and a rupture life in excessof 100 hours under a load of 8,000 p.s.i. at a temperature of about 1800F. in

Example 7 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 28 percent of chromium, about 5 percent of tungsten,about 8 percent of tantalum, about 2.0 percent of titanium, about 0.5percent of Zirconium, about 0.7 percent of carbon, and the balanceessentially cobalt, all percentages by weight, were prepared in the samemanner as set forth in Example 1.

The test bars of this example had an elongation of 1 percent at roomtemperature under a tensile stress of 120,000 p.s.i. a

The test bars of this example had a rupture life in excess of 100 hoursunder a load of 20,000 p.s.i. at a temperature of about 1600 F. in air,a rupture life in ex cess of 100 hours under a load of 10,000 p.s.i. ata temperature of about 1700 F. in air, and a rupture life in excess of100 hours under a load of 5,000 p.s.i. at a temperature of about 1800 F.in air.

Example 8 A 5 pound alloy melt and test bars of the same di- 7 weight,were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of about 2 percent atroom temperature under a tensile stress of 113,000 p.s.i.

The test bars of this example had a rupture life in excess of 250 hoursunder a load of 22,000 p.s.i. at a temperature of about 1600 F. in air,a rupture life of about 329 hours under a load of 15,500 p.s.i. at atemperature of about 1700 F., and a rupture life in excess of 63 hoursunder a load of 8,000 p.s.i. at a temperature of about 1800 F. in air.

Example 9 A pound alloy melt and test bars of the same dimensions as setforth in Example 1 of a cobalt base metal alloy composition containingabout 21.5 percent of chromium, about 9.6 percent of tungsten, about 1.2percent of tantalum, about 0.3 percent of titanium, about 0.45 percentof carbon, about 1.5 percent of silicon, about 0.28 percent ofmanganese, about 1.5 percent of nickel, about 1.5 percent of iron, andthe balance essentially cobalt, all percentages by weight, were preparedin the same manner as set forth in Example 1.

The test bars of this example had an elongation of about 3.3 percent atroom temperature under a tensile stress of 118,000 p.s.i.

The test bars of this example had a rupture life in excess of 233 hoursunder a load of 13,000 p.s.i. at a temperature of about 1700 F. in air,and a rupture life in excess of 154 hours under a load of 10,000 p.s.i.at a temperature of about 1800 F. in air.

Example 10 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 21.5 percent of chromium, about 9.7 percent oftungsten, about 10.6 percent of tantalum, about 0.4 percent ofZirconium, about 0.3 percent of titanium, about 0.75 percent of carbon,and the balance essentially cobalt, all percentages by weight, wereprepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 1.1 percent at roomtemperature under a tensile stress of 110,000 p.s.i.

The test bars of this example had a rupture life in excess of 59 hoursunder a load of 17,000 p.s.i. at a temperature of about 1800 F. in air.

Example 11 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 21 percent of chromium, about 9 percent of tungsten,about 9 percent of tantalum, about 0.2 percent of titanium, about 0.85percent of carbon, about 1.0 percent of molybdenum, and the balanceessentially cobalt, all percentages by weight, were prepared in the samemanner as set forth in Example 1.

The test bars of this example had a rupture life in excess of 51 hoursunder a load of 15,000 p.s.i. at a temperature of about 1800 F. in air.

Example 12 manner as set forth in Example 1.

The test bars of this example had an elon ation or" 6 about 3.3 percentat room temperature under a tensile stress of 142,800 p.s.i.

The test bars of this example had a rupture life in excess of 51 hoursunder a load of 15,000 p.s.i. at a temperature of about 1800 F. in airand a rupture life in excess of 137 hours under a load of 20,000 p.s.i.at a temperature of about 1700 F. in air.

Example 13 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 20 percent of chromium, about 10 percent of tungsten,about 10 percent of tantalum, about 0.9 percent of carbon, about 0.3percent of silicon, about 0.5 percent of manganese, about 0.5 percent oftitanium, and the balance essentially cobalt, all percentages by weight,were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 2.5

ercent at room temperature under a tensile stress of 139,000 p.s.i.

The test bars of this example had a rupture life in excess of 60 hoursunder a load of 22,500 p.s.i. at a temperature of about 1700" F. in airand a rupture life in excess of 41 hours under a load of 17,000 p.s.i.at a temperature of about 1800" F. in air.

Example 14 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 20 percent of chromiul. about 7.5 percent of tungsten,about 7.5 percent of tantalum, about 0.1 percent of titanium, about 0.85percent of carbon, about 0.01 percent of boron, and the balanceessentially cobalt, all percentages by weight, were prepared in the samemanner as set forth in Example 1.

The test bars of the example had an elongation of 1.6 percent at roomtemperature under a tensile stress of 142,200 p.s.i.

The test bars of this example had a rupture life in excess of 134 hoursunder a load of 22,500 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 51 hours under a load of 17,000 p.s.i.at a temperature of about 1800" F in air.

Example 15 2.5 percent at room temperature under a tensile stress of125,600 p.s.i.

The test bars of this example had a rupture life in excess of 166 hoursunder a load of 22,500 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 68 hours under a load of 17,000 p.s.i.at a temperature of about 1800 F. in air.

Example 16 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 10 percent of tungsten,about 10 percent of tantalum, about 0.1 percent of titanium, about 0.85percent of carbon, about 0.01 percent of boron, about 5 percent of iron,and the balance essentially cobalt, all percentages by weight, wereprepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of 1.6

7 percent at room temperature under a tensile stress of 137,500 psi.

The test bars of this example had a rupture life in excess of 59 hoursunder a load of 15,000 psi. at a temperature of about 1800 F. in air anda rupture life in excess of 30 hours under a load of 8,000 psi. at atemperature of about 2000 F. in air.

Example 17 A pound alloy melt and test bars of tr e same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent or" chromium, about percent of tungsten,about 10 percent of tantalum, about 0.1 percent of titanium, about 0.85percent of carbon, about 0.01 percent of boron, about 5 percent ofnickel, and the balance essentially cobalt, all percentages by weight,were prepared in be same manner as set forth in Example 1.

The test bars or" this example had an elongation of 3.3

percent at room temperatu e under a tensile stress of 134,000 psi. 7 Thetest bars of this example had a rupture life in excess of 56 hours undera load of 15,000 psi at a temperature of about 1800 F. in air and arupture life in excess of 25 hours under a load of 8,000 p.s.i. at atemperature of about 2000 F. in air.

Example 1 8 A5 pound alloy metal and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 10 percent of tungsten,about 10 percent of tantalum, about 0.1 percent of titanium, about 1.3percent of carbon, and 0.01 percent of boron, and the balanceessentially cobalt, all percentages by Weight, were prepared in the samemanner as set forth in Example 1.

The test bars of this example had an elongation of 1.7 percent at roomtemperature under a tensile stress of 145,500 psi.

The test bars of this example had a rupture life in excess of 41 hoursunder a load of 15,000 psi at a temperature of about 1800 F. in air.

Example 19 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chro miurn, about 10 percent of tungsten,about 10 percent of tantalum, about 0.1 percent of titanium, about 0.2percent of boron, about 0.85 percent of carbon, and the balanceessentially cobalt, all percentages by weight, were prepared in the samemanner as set forth in Example 1.

The test bars of this example had an elongation of 0.8 percent at roomtemperature under a tensile stress of 135 000 psi.

The test bars of this example had' a rupture life in excess of 50 hoursunder a load of 15,000 p.s.i. at a temperature of about 1800 F. in air.

Example A 5 pound alloy melt and test bars of the same dimensions as setforth in Example 1 of a cobalt base metal alloy composition containingabout 22' percent of chromium, about 8 percent of tungsten, about 8percent of tantalum, about 3 percent of columbium, about 0.1 percent oftitanium, about 0.85 percent of carbon, about 0.01 percent of boron, andthe balance essentially cobalt, all percentages by Weight, were preparedin the same manner as set forth in Example 1.

The test bars of this example had an elongation of 0.95 percent at roomtemperature under a tensile stress of 125,000 p.s.i.

The test bars of the example had a rupture life in excess of 62 hoursunder a load of 15,000 psi. at a temperature of about 1800" F. in air.

Example 21 A 5 pound alloy melt and test bars or" the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 12.5 percent of tungsten,about 3 percent of tantalum, about 1 percent of columbium, about 0.1percent of titanium, about 1 percent of carbon, about 0.01 percent ofboron, and the balance essentially cobalt, all percentages by weight,were prepared in the same manner as set forth in Example 1.

The test bars of this example had an elongation of .8 percent at roomtemperature under a tensile stress of 137,- 000 psi.

The test bars of this example had a rupture life in excess of 22 hoursunder a load of 15,000 psi. at a temperature of about 1800 F. in air.

Example 22 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 12.5 percent of tungsten,about 3 percent of tantalum, about 1 percent of columbium, about 0.1percent of titanium, about 1 percent of carbon, about 0.01 percent ofboron, about 5 percent of nickel, and the balance essentially cobalt,all percentages by wei ht, were prepared in the same mariner as setforth in Example 1.

The test bars of this example had an elongation of 3 percent at roomtemperature under a tensile stress of 131,900 psi.

The test bars of this example had a rupture life in excess of 41 hoursunder a load of 15,000 psi. at a temperature of about 1800 F. in air.

Example 23 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 8 percent of tungsten,about 8 percent of tantalum, about 1 percent of colurnbium, about 0.1percent of titanium, about 0.85 percent of carbon, about 0.01 percent ofboron, and the balance essentially cobalt, all by weight, were preparedin the same manner as set forth in Example. l.

The test bars of this example had an elongation of 1.6 percent at roomtemperature under a tensile stress of 132,100 psi.

The test bars of this example had a rupture life in excess of 277 hoursunder a load of 20,000 psi. at a temperature of about 1700" F. in air, arupture life in excess of 128 hours under a load of 15,000 psi. at atemperature of about 1800 F. in air.

Example 24 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 22 percent of chromium, about 8 percent of tungsten,about 8 percent of tantalum, about 1 percent of columbium, about 0.1percent of titanium, about 0.85 percent of carbon, about 0.01 percent ofboron, about 5 percent of iron, and the balance essentially cobalt, allpercentages by Weight, were prepared in the same manner as set forth inExample 1.

The test bars of this example had an elongation of 0.8 percent at roomtemperature under a tensile stress of 127,600 p.s.i.

The test bars of this example had a rupture life in excess of 33 hoursunder a load of 15,000 p.s.i. at a emperature of about 1800 F. in airand a rupture life in excess of 19 hours under a load of 5,000 psi. at atemperature of about 2000 F. in air.

Example 25 A 5 pound alloy melt and test bars of the same dimen- 9 sionsas set forth in Example 1 of a cobalt base metal alloy compositioncontaining about 25 percent of chromiurn, about 10 percent of tungsten,about percent of tantalum, about 2 percent of columbium, about 0.85percent of carbon, about 0.1 percent of titanium, about 0.01 percent ofboron, about 5 percent of iron, and the balance essentially cobalt, allpercentages by weight, were prepared in the same manner as set forth inExample 1.

The test bars of this example had an elongation of 1.6 percent at roomtemperature under a tensile stress of 139,400 p.s.i.

The test bars of this example had a rupture life in excess of 53 hoursunder a load of 15,000 p.s.i. at a temperature of about 1800 F. in airand a rupture life in excess of 21 hours under a load of 5,000 p.s.i. ata temperature of about 2000 F. in air. The oxidation penetration was0.017 mil per side per hour after 100 hours in moving air at 2000 F. and0.07 mil per side per hour after 24 hours in moving air at 2100 F.

Example 26 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 18 percent of chromium, about 8.6 percent of tungsten,about 2.5 percent of tantalum, about 0.6 percent of titanium, about 0.1percent of zirconium, about 0.49 percent of carbon, about 0.2 percent ofsilicon, about 2.5 percent of nickel, about 2.5 percent or" iron, andthe balance essentially cobalt, all percentages by Weight, were preparedin the same manner as set forth in Example 1.

The test bars of this example had an elongation of 3 percent at roomtemperature under a tensile stress of 100,000 p.s.i.

The test bars of his example had a rupture life in excess of 250 hoursunder a load of 22,000 p.s.i. at a temperature of about 1600 F. in airand a rupture life in excess of 100 hours under a load of 10,000 p.s.i.at a temperature of about 1800 F. in air.

Example 27 A 5 pound alloy melt and test bars of the same dimensions asset forth in Example 1 of a cobalt base metal alloy compositioncontaining about 20 percent of chromium, about 11 percent of tungsten,about 0.5 percent of tantalum, about 2.9 percent of titanium, about 0.1percent of zirconium, about 0.7 percent of carbon, about 0.4 percent ofsilicon, about 0.5 percent of nickel, about 0.5 percent of iron, and thebalance essentially cobalt, all percentages by weight, were prepared inthe same manner as set forth in Example 1.

The test bars of this example had an elongation of 8 percent at roomtemperature under a tensile stress of 115,000 p.s.i.

The test bars of this example had a rupture life in excess of 100 hoursunder a load of 15,000 p.s.i. at a temperature of about 1700 F. in airand a rupture life in excess of 100 hours under a load of 10,000 p.s.i.at a temperature of about 1800 F. in air.

The above detailed description has been given for clearness ofunderstanding only. No unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

I claim:

1. A metal alloy consisting essentially of, by weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, from about0.01 to about 3 percent of titanium, from about 0.6 to about 1.3 percentof carbon, and the balance cobalt.

2. A metal alloy consisting essentially of, by Weight, from about 16 toabout 25 percent of chromium, from about 7.5 to about 12.5 percent oftungsten, from about 7 10 to about 11 percent of tantalum, from about0.08 to about 0.5 percent of titanium, from about 0.6 to about 1 percentof carbon, and the balance cobalt.

3. A metal alloy consisting essentially of, by Weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, up to about 3percent of columbium, with the columbium content not more than about 50percent of the amount of tantalum in the alloy, from about 0.01 to about3 percent of titanium, from about 0.6 to about 1.3 percent of carbon,and the balance cobalt.

4. A metal alloy consisting essentially or", by weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent of tunsten, from about 0.5 to about 20 percent of tantalum, from about 0.01 toabout 3 percent of titanium, up to about 3.5 percent of molybdenum, withthe molybdenum content not more than about 50 percent of the amount oftungsten in the alloy, from about 0.6 to about 1.3 percent of carbon,and the balance cobalt.

5. A metal alloy consisting essentially of, by Weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, from about0.01 to about 3 percent of titanium, up to about 0.2 percent of boron,from about 0.6 to about 1.3 percent of carbon, and the balance cobalt.

6. A metal alloy consisting essentially of, by weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, up to about 3percent of columbium, With the columbium content not more than about 50percent of the amount of tantalum in the alloy, from about 0.01 to about3 percent of titanium, zirconium in an amount such that, if the amountof titanium is more than 0.5 percent, the combined amount of titaniumand zirconium is equal to or less than 3 percent, and if the amount oftitanium is equal to or less than 0.5 percent, titanium is more thanabout 70 percent of zirconium, up to about 0.2 percent of boron, up toabout 3.5 percent of molybdenum, with the molybdenum content not morethan about 50 percent of the amount of tungsten in the alloy, from about0.6 to about 1.3 percent of carbon, and the balance cobalt.

7. A metal alloy consisting essentially of, by Weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, from about0.01 to about 3 percent of titanium, zirconium in an amount such that,if the amount of titanium is more than 0.5 percent, the combined amountof titanium and zirconium is equal to or less than 3 percent, and if theamount of titanium is equal to or less than 0.5 percent, titanium ismore than about 70 percent of the zirconium, from about 0.6 to about 1.3percent of carbon, up to about 1.5 percent of silicon, up to about 5percent of nickel, up to about 5 percent of iron, and the balancecobalt.

8. A metal alloy consisting essentially of, by weight, from about 15 toabout 28 percent of chromium, from about 5 to about 15 percent oftungsten, from about 0.5 to about 20 percent of tantalum, up to about 3percent of columbium, with the eolumbium content not more than about 50percent of the amount of tantalum in the alloy, from about 0.01 to about3 percent of titanium, zirconium in an amount such that, if the amountof titanium is more than 0.5 percent, the combined amount of titaniumand zirconium is equal to or less than 3 percent, and if the amount oftitanium is equal to or less than 0.5 percent, titanium is more thanabout 70 percent of the zirconium, up to about 0.2 percent of boron, upto about 3.5 percent of molybdenum, with the molybdenum content not morethan about 50 percent of the amount of tungsten in the alloy, from about0.6 to about 1.3 percent of carbon, up to about 1.5 percent of silicon,up

11 to about 5 percent of nickel, up to about 5 percent of iron and thebalance cobalt.

9. A metal alloy consisting essentially of, by weight, from about 16 toabout 25 percent of chromium, from about 7.5 to about 12.5 percent oftungsten, up to about 3.5 percent of molybdenum, from about 7 to about11 percent of tantalum, up to about 3 percent of colurnbium, from about(1.08 to about 0.5 percent of titanium, zirconium in an amount such thatthe amount of titanium is more than 70 percent, the amount of zirconiumin the alloy, from about 0.6 to about 1 percent of carbon, up to about0.2 percent of boron, up to about 1.5 percent of silicon, up to about2.5 percent of nickel, up to about 2.5 percent of iron, and the balancecobalt.

7 References Cited in the file of this patent UNITED STATES PATENTS2,247,643 Rohn et a1 July 1, 1941 Johnson July 18, Binder July 20,Malcolm Nov. 20,

FOREIGN PATENTS Great Britain Mar. 6, Great Britain Ian. 21, Canada June25,

OTHER REFERENCES Materials and Methods, September 1953; Number 260,

page 139.

1. A MATERIAL ALLOY CONSISTING ESSENTIALLY OF, BY WEIGHT, FROM ABOUT 15TO ABOUT 28 PERCENT OF CHROMIUM, FROM ABOUT 5 TO ABOUT 15 PERCENT OFTUNGSTEN, FROM ABOUT 0.5 TO ABOUT 20 PERCENT OF TANTALUM, FROM ABOUT0.01 TO ABOUT 3 PERCENT OF TITANIUM, FROM ABOUT 0.6 TO ABOUT 1.3 PERCENTOF CARBON, AND THE BALANCE COBALT.